GC VILLAGE — If the Colorado River system’s conditions are just right later this year, there could be another experimental flood through Grand Canyon next January.
The Glen Canyon Adaptive Management Work Group, a federal advisory group to Interior secretary Gale Norton, recommended another artificial flood in Grand Canyon to help restore its natural environment and help the endangered native fish species, the humpback chub.
The Glen Canyon Dam’s floodgates were opened in March 1996 for the first experimental flow with intentions of churning up accumulated silt and redistributing sediment on river banks, sandbars and side canyons.
Researchers believed that sediment accumulated from year to year deep in the Colorado River channel, which was the basis for the 1996 flood. However, new research shows a different scenario with the river holding sand on its bed for only a few months, not a few years.
The Bureau of Reclamation recommends the next experimental flow to take place in January, but only under the right conditions.
"These experimental flow recommendations are based on the substantial new knowledge gained over the past five years from implementation of the adaptive management process," said Barry Gold, chief of the Grand Canyon Monitoring and Research Center.
The group’s recommendation to be forwarded to Norton will offer four options for special releases, depending on various circumstances and new sediment into the Grand Canyon from Paria River tributary flows during the late summer and fall monsoon season. The special releases need that sediment for rebuilding beaches and for the humpback chub.
The flows would be about 41,000 cubic feet per second, depending upon Lake Powell levels and the availability to use the full capacity of the Glen Canyon Dam power plant. Under full power plant generation conditions, the maximum output is approximately 31,000 cfs.
The 1996 flows were 45,000 cfs. If there are no significant sediment inputs from July through December, the new test will be staged in the first year that future fall tributary sediment flows do occur.
Besides improving the river ecosystem and native fish populations, the experimental flow’s secondary purpose is to improve trout fishing around Lees Ferry. Densities of rainbow trout at Lees Ferry would be reduced, which is expected to improve survival and growth of the remaining fish and preserving the blue-ribbon character of that fishery.
Each scenario includes the mechanical removal of salmonid fish near the confluence of the Little Colorado River and the Colorado River. Primarily rainbow trout, the fish are thought to prey on or compete with the humpback chub. The process would involve electroshocking the trout and then collecting them to reduce their population.
In addition, the experimental flow proposal includes winter fluctuating flows to disrupt the spawning and recruitment of young trout.
The advisory group also is recommending an analysis be undertaken to develop a population of the humpback chub to preserve its DNA strain. Surveys estimate there are just 2,000 humpback chubs in the Canyon, down from 8,300 in 1993.
"There is still uncertainty about the cause of the decline in the humpback chub population," said Randall Peterson, manager of the Bureau of Reclamation’s Adaptive Management Division in Salt Lake City. "These recommended experiments are an important step in answering those questions."
The advisory group also reaffirmed a decision made this past year to attempt to remove brown trout from the Bright Angel Creek area near Phantom Ranch. Brown trout are a known predator on the humpback chub.
The National Park Service will test the ability to collect the non-native fish through the use of a weir across the creek. This is a physical device that will impede the ability of the fish to move out of the Colorado River into the creek to spawn.
After briefly testing the ability to use the weir to collect the fish, the NPS will remove the weir and develop an environmental assessment on the plans in compliance with the National Environmental Policy Act.
Public comment and involvement in this planning process will be included in the NPS studies. Details concerning the test and upcoming studies are expected soon from the NPS.
At last week’s meeting, Peterson was pleased to see progress.
"We commend the stakeholders, scientists, and members of the public for working together to address new information about Grand Canyon’s resources," he said. "Their commitment to a collaborative process within applicable laws is evidence the program is working as Congress intended."